What nodes clamp your values?
Most nodes should not.

Cycles works under a scene referred rendering model, which means that there is no notion of white or black, but merely a range of values that traverse from some low value to a theoretically (within the quantization limits of 32 bit float) infinite range of light.

As such, all nodes should never clamp, or they will not deal with the scene referred data correctly.

Some by design might map such as the Range node. The Colour Ramp sadly is based on a fixed 0.0-1.0 range which greatly diminishes it's usefulness with modern renderers.

The precise answer to the best of my knowledge, is that there is no comprehensive listing. This is something anyone could map out however via the wiki with a table and a little help from contributions.